Overheating worry

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bulgarianfalco · #1 Post by **bulgarianfalco** » Mon Jul 10, 2017 9:52 am

Help again please guys - my falco is overheating - on the motorway it goes down to 83/4 ( I'm sure it used to be 78) but around town it quickly gets up to 120 plus!!

Checking the coolant level, I noticed a split in the clear level-checking tube, so I replaced this and topped up with water, thinking that must be it. No change - might I have to bleed the cooling system or something?

Both fans seem to be working fine (although worryingly they stop when you turn the ignition off). I turned back on today, and the fans bought it down from 119 to 105 at a standstill with the engine off.

Might have answered my own question there, as that sounds like the thermostat (or something) making the fan not work at a low enough temperature.

Btw, just fitted some Metzeler Z8's and very happy with them - feeling more confident than with the previous Sportsmarts.....

Dalemac · #2 Post by **Dalemac** » Mon Jul 10, 2017 5:00 pm

My falco is a steady 68 degrees C on the motorway, but it quickly gets up to 93 around town in this kind of weather.

Fans should come on around 92 plus or minus a couple of degrees.

The cooling system is surprisingly simple - a couple of radiators, a pump, a thermostat, and some thermistors to turn the fans on when it's getting a bit warm.

The fans turn off automatically when the ignition is off. If you want to have them on for a few minutes, you'll need to keep the ignition on. Bearing in mind that coolant won't be circulating through the radiators, so not a whole lot of point in doing this.

I'd always recommend doing a coolant change if you haven't done it for a while. It's only supposed to last two years, and is a very simple job to do.

First port of call would be to check what temperature the fans come on at. If it's over 100, you'll probably want to look at replacing the thermistors.

If the bike is unable to keep itself cool at a standstill with the engine running, by cycling the fans on and off every few minutes to drop the temperature, you may have another issue, such as a broken pump, or even a leaky head gasket.

But first things first - change the coolant and let us know the temperature the fans come on at, and whether it can keep itself cool at tickover.

Dalemac · #3 Post by **Dalemac** » Mon Jul 10, 2017 5:06 pm

By the way - a good way to check that the pump is working is to run the bike to the point the fans come on, hit the killswitch and then let the fans cool the coolant in the radiators until the fans switch off.

Then start the engine again. If the pump is working, the temperature should drop by at least a few more degrees, as the coolant in the radiators (which is now significantly cooler than the coolant in the rest of the system) will flow over the temperature sensor, which will cool it.

Obviously it won't be long until it's heating back up again, but i've always found it to be a good test.

bulgarianfalco · #4 Post by **bulgarianfalco** » Mon Jul 10, 2017 7:04 pm

cheers for that, I was after a way to decide between the pump and the thermostat, rather than just replacing both....I'll give this a try in the morning, ta.

bulgarianfalco · #5 Post by **bulgarianfalco** » Tue Jul 11, 2017 8:00 am

right, started up and fans not coming on until 115 deg so, there's the problem. Killed the engine and fans cooled down to 100 deg when they cut out again. Restarted after 5 mins and temperature not immediately rising, altbhough not actually falling, suggesting the pump is working?.....

So, do I need thermostats or thermistodors (or something) and any suggestions where best to get these mail order?

All suggestions gratefully received :)

Dalemac · #6 Post by **Dalemac** » Tue Jul 11, 2017 9:38 am

It does sound to me like your fans are coming on too late and cutting out too early.

I'm no electrical guru (That's D-Rider), but I believe that thermistor work by changing resistance as temperature changes. Presumably, the falco uses the negative temperature coefficient type thermistor, so as the temperature rises, the resistance decreases.

What is probably happening is the resistance is not changing at the right temperature, so the fans are not coming on or cutting out at the right point.

For reference - my fans usually come on at around 92 degrees and cut out around 89 degrees. They'll cycle on/off every minute or so.

For info - There are two temperature sensors - one in each cylinder head. The front temperature sensor sends the temperature to the dash, the rear temperature sensor sends the temperature to the ECU.

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I'd start simple and just replace the thermistor to begin with (manual calls it a thermistor, parts diagram calls it a thermal switch) - part 17 on this list of bits:

https://www.ultimateparts.net/aprilia/c ... 13&i=18424

Though I wouldn't buy it from ultimate parts - their shipping is ludicrous, even within the UK.

Id give Griff a call or drop him an email (http://www.apriliaperformance.co.uk/) - He should post to you. You can also run the issue past him as well for a second opinion.

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Regarding the pump - There is another way to check it is working, but I'm hesitant to say at this point as there is an element of risk involved.

fatboy · #7 Post by **fatboy** » Tue Jul 11, 2017 5:46 pm

Your fan switch is fucked !!!!!!!
Mine did something similar, the kick in temp got higher and higher, the fans not kicking in until 99 or 101.
new switch fitted fans come on at 89 and switch off at 87.
Do it, you know it makes sense

blinkey501 · #8 Post by **blinkey501** » Tue Jul 11, 2017 8:13 pm

fatboy wrote:Your fan switch is fucked !!!!!!!
Mine did something similar, the kick in temp got higher and higher, the fans not kicking in until 99 or 101.
new switch fitted fans come on at 89 and switch off at 87.
Do it, you know it makes sense

Fitted a brand new switch to a falco recently and the fans kick in at 99 degrease with the new switch.

My mille r, futura and the many falco's I have owned are the same.

fatboy · #9 Post by **fatboy** » Wed Jul 12, 2017 5:37 pm

There are thermo switches with different kick in settings, Mine came from AP, a genuine Aprilia part.
Industry standard is fans on at 98, off at 95, I prefer the lower settings, cant help but think they are a little kinder to the motor

#10 Post by **mangocrazy** » Wed Jul 12, 2017 6:49 pm

You can get thermoswitches that operate at lower temperatures than that, but they're all in car type sizes as far as I know. Does anyone know off-hand what the thread size and pitch of the Aprilia item is?

fatboy · #11 Post by **fatboy** » Fri Jul 14, 2017 7:42 pm

I will look in the shed tomorrow and see if I have still got the redundandant item, will report back...

blinkey501 · #12 Post by **blinkey501** » Fri Jul 14, 2017 9:31 pm

fatboy wrote:Mine came from AP, a genuine Aprilia part.

Mine came from Yorkshire aprilia.

bulgarianfalco · #13 Post by **bulgarianfalco** » Sun Jul 16, 2017 6:29 am

Ahem, turns out Griff was right in suggesting low coolant level causing all the above symptoms - apparently topping up the expansion tank is not at all the same as topping up the pressurised filler cap - which is obvious with a moment's intelligent thought......and now all is back to normal.

Big thanks to all contributors :)

Still wouldn't mind a 65 degree thermostat though, to cope with routine mid 30's throughout the summer !

fatboy · #14 Post by **fatboy** » Mon Jul 17, 2017 6:18 pm

Good to hear that all is well with the bike, we learn things we thought we knew and we can step back and laugh at our selves